THE PENNSYLVANIA STATE UNIVERISTY DEPARTMENT OF GEOSCIENCES Estimating the Pleistocene Slip Rate of the Owens Valley Fault, California

Slip rates of the right-lateral Owens Valley Fault lie at the center of an ongoing debate over the rheology and mechanics of lithospheric deformation in eastern California. Slip rates determined from paleoseismic records of surface rupture yield Late Pleistocene – Holocene rates of < 1mm/yr to ~2 mm/yr. The decadal velocity field across the valley, however, approaches ~6 mm/yr of right-lateral shear. The difference between these measures of crustal deformation has been interpreted to reflect a viscoelastic transient following the 1872 Owens Valley earthquake. In order to test whether paleoseismic estimates of slip rate are representative of the long-term behavior of the fault, we determined average slip rates using an offset basalt flow on the edge of Crater Mountain. The flow margin on the NE side of the volcanic cone exhibits an apparent right-lateral separation across the trace of the Owens Valley fault. We conducted ground penetrating radar surveys across the flow margin in order to refine the geometry of the contact between the flow and modern alluvium. Results suggest that the flow is not significantly buried beneath alluvium, and reconstruction of the flow suggests approximately 150-390 m of right-lateral offset, depending on the initial geometry of the flow. West of the fault, the flow overlies a remnant alluvial fan with surface and soil characteristics similar to alluvial fans above the Fish Springs Fault dated to ~130 ka. 3 He exposure ages from basalt flows located on the southern flanks of Crater Mountain range between ~110 and 115 ka, and are assumed to be the timing of the last outpouring of basalt. Using these